Synthesis of FeN(4) at 180 GPa and its crystal structure from a submicron-sized grain

Iron tetra­nitride, FeN(4), was synthesized from the elements in a laser-heated diamond anvil cell at 180 (5) GPa and 2700 (200) K. Its crystal structure was determined based on single-crystal X-ray diffraction data collected from a submicron-sized grain at the synchrotron beamline ID11 of ESRF. The compound crystallizes in the triclinic space group P [Image: see text]. In the asymmetric unit, the Fe atom occupies an inversion centre (Wyckoff position 1d), while two N atoms occupy general positions (2i). The structure is made up from edge-sharing [FeN(6)] octa­hedra forming chains along [100] and being inter­connected through N—N bridges. N atoms form catena-poly[tetraz-1-ene-1,4-di­yl] anions [–N=N—N—N–](∞) (2−) running along [001]. In comparison with the previously reported structure of FeN(4) at 135 GPa [Bykov et al. (2018). Nat. Commun. 9, 2756], the crystal structure of FeN(4) at 180 GPa is similar but the structural model is significantly improved in terms of the precision of the bond lengths and angles.